I learned enough to know when to call IBM for support, but with that experience it wouldn't be too difficult to find another job managing one.
I remember 12+ years ago, my old boss bitching about working on an AS/400, then he'd hire his brother (who worked on them for years) to come out to do very simple stuff for quite a high premium.
I just wish they weren't so proprietary, but at the same time, I am glad they are. It's been a love hate relationship.
Now I work with an AIX system. Unix under the hood, but IBM still has a stranglehold on it. Both tanks though.